Separation of oxygen from the air.



L. BERGFELD.

SEPARATION 0F OXYGEN FROM THE AIR.

APPLICATION FILED SEPT. so, 191s.

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L. BERGFELD.

SEPARATION 0F OXYGEN FROM THE AIR.

APPLICATION FILED SEPT. ()A 1913. 1,1 20,436. Patented Dec. 8, 1914.

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LUDWIG 'BERGFELD, OF DURLACH, NEAR KARLSRUHE, GERMANY.

SEPARATION OF OXYGEN FROM THE AIR.

Specification o1 Letters Patent.

Patented Dec. 8, 1914.

' Application Ied September 30, 1913. Seriall No. 792,622.

To all whom it may concern:

Be it known thatI, LUDWIG BERGFELD, a subject of the German Emperor, residing in Durlach, near Karlsruhe, in Germany, have invented certain new and useful Improvements in the Separation of Oxygen from the Air, of which the following is a specification.

This invention is for improvements in or relating to the separation of oxygen from the air.

According to this invention the process for obtaining oxygen from the air by a continuous cycle of operations consists in producing a high oxid of nitrogen by the action of air on a lower oxid and then decomposing the higher oxid produced into oxygen and the lower oxid, the process being repeated any number of times.

A feature of the present invention consists in the employment of sulfuric acid as an intermediate agent to effect the decomposition of the high oxid of nitrogen, whereby there are obtained as products of the reaction nitrosulfonic acid, oxygen and water, from the former of which, namely the nitrosulfonic acid, sulfuric'acid and the low oxid of nitrogen are regenerated by the action of water.

In such a process a further feature of this invention consists in utilizing the heat of the hot Huid for heating the cool fluid and at the same time cooling the hot fluid, as for example by passing the two liuids in opposite directions through two adjacent chambers separated by a thin wall ofconducting material.

Throughout this specification rthe term fluid is used to mean either liquids or gases or both liquids and gases.

ln carrying out the invention, in order to effect an interchange of heat between gases or between gases and liquids when the said iuids do not come into direct contact with one another, there can be employed an intermediate liquid. 'Furthen in addition to the interchange of heat that ma take place between two substances on ai.

.temperature may be transferred to a. coolersubstance in exactly the same manner as heat is 'transferred from the body at a higher temperature to the said cooler substance. ln

ference in temperature, it lsf-also possible acinto chemical energy during the course of a y reaction that takes place in the said second set of substances. There can also be employed in this process a separate auxiliary transmitter of `heat for effecting the heat interchange treated, namely the one to be cooled and the one to be heated, the said auxiliary transmitter being for example in the shape of small solid particles composed of a suitable substance such as quartz.

The basis of this invention is the wellknown fact that, on being heated to above its .boiling point, nitric acid decomposes and gives olf the oxygen according to the following equation :k

1t combines with water and on the other' hand forms nitrosyl sulfuric acid from the nitrogen peroxrd, with further separation of oxygen according to the following .equation on zmsowznogasof( o (No) From the nitrosyl sulfuric acid, sulfuric acid and nitrous anhydrid are regenerated by the action of water,"thus:-

The nitrous anhydrid reacts with airvand water to reform nitric acid according tothe It will be seen therefore that the original starting materials of the process are thus reformed quantitatively.

Preferably in carrying the process into effect the reactions are carried out in acbetween the two substances cordance with the principle of interchangel i of heat, a strict continultyjof the cycle during thel whole process being observed.v According to this principle a substance to be heated, which will be designated the secondary stream element of the heat exchanging device, receives heat from a substance which is to be cooled, this latter being designated the primary stream element; this exchange of heat is brought about by caus' ing the said materials to pass over one another in counter current, the materials being separated from each other by a sufliciently long and thin partition which is a good conductor ofI heat. In the present case the condition of equivalence is present,

as the air supplied is equal to that carried v dependence on the temperature. 'Io this end, the water vapor or steam is generated from dilute sulfuric acid, the boiling poi-nt of which rises as is wellnknown with the concentration, and the liquefaction of the steam is effected by means of sulfuric acid, in so far as it is not a question ofv condensaf tion or vaporization below the boiling point.

Nitric acid can also be evaporated and condensed in the same manner. For example, if a mixture of equal parts of water, sulfuric acid and nitric acid be heated, the evaporation of the latter inthe interval from about 123O C. to nearly 160O C. ap-

proximately keeps pace, as the temperature increases, with the evaporation of the water. The exchange of heat between two gases, or between a gas and liquid not in direct contact with the latter, is preferably eected by making use of liquids as intermediaries; the liquid is brought into thorough contact with the gas by means of a suitable stirring device.

The process can be carried out in the following manner z-Nitric acid vapors heated ,to the desired temperature in an apparatus designed to give effect to the principle of exchange ofv heat, are caused to pass over fairly concentrated, nearly boiling, sulfuric acid of the same temperature, both flowing as primary currents, until the sulfuric acid is saturated at about 145o C. with water y and oxids of nitrogen while oxygen remains over the liquid and is carried away. The nitrosyl sulfuric acid then passes into the secondary current of the heat exchange apparatus and there discharges vnitrous acid and Water, the latter two being preferably discharged at several places, combined and mixed with air.

The mixture of oxids of nitrogen, air and water, acts as the primary current as regards exchange of heat to thetsecondary current of the air supplied for the process and the vapors of nitric acid and any liquid nitric acid developed therefrom; the nitric acid resulting from the combination of the mixture of voxids of nitrogen, airand water, is then conveyed to the stream of sulfuric acid liowing as a primary current. This stream of sulfuric and nitric acids, cooled to the greatest possible extent, atthe end of its course as a primary current, again enters the secondary current and here supplies the nitric acid vapors for the formation of nitrosyl sulfuric acid, as already described. The cycle is thus closed.

It -must be borne in mind that all the reacting substances taking part in this.process are heated or cooled merely by exchange yof heat, and the process must be carried out in such manner that the given stages of the primary current correspond exactly to those of the secondary current. In order to remove the last traces of nitric acid, the discharged gases can be submitted to a separate cooling arrangement in accordance with the heat exchange principle or they can be washed with water or a solution of ammonium nitrate etc.

It is immaterial forthe process which of any other possible methods are selected. For example nitric acid may be volatilized by steam (the steam being generated from dilute sulfuric acid or acid nitrates) in an apparatus working according to the heat exchange principle and the nitric acid vapors may be deprived of water before the formation of nitrosyl sulfuric acid by means of a primary current of sulfuric acid or phosphoric acid, Vor a corresponding excess of sulfuric acid could be employed during the formation of the nitrosyl sulfuric acid.

A- practical method of carrying this invention into effect will now be described with the aidlof the accompanying diagrammatic sketches, of which-- Figure l illustrates the arrangement of the conduits conveying the reacting substances and the products of reaction and the direction of the flow of the currents through the same, and Figs. 2 to 6 details in the construction of the said conduits.

Referring now to F ig. 1, full lines indicate Apipes conveying currents of liquid, dotted lines gas and steam pipes, the direction of the currents being indicated by arrows. The pipes Nos. I to VI ofthe construction hereinafter described, are secured to one and the same rotatable spindle, the extreme range of temperature at which the pipes are maintained gradingvfrom about 150o C. at one end to 280c C. at the other end.v

In pipe I, the current of sulfuric acid flowing' in the primary direction withdraws water from a current of nitric acid vapors and steam flowing in the secondary direction. Nitrogen peroxid NO2, and oxygen escape, and are conducted as a primary current into pipe III, where they meet a current of sulfuric acid also flowing in the primary direction; here the sulfuric acid absorbs the NO2, while the oxygen liberated escapes. The liquid from pipe I enters pipe II as a secondary current, and here discharges its water in the form of vapor, for the most part in the direction of the secondary current and as regards a small portion in the primary direction. The residual liquid is returned to pipe I. From pipe III, nitrosyl sulfate passes in the secondary direction into pipe IV, where it meets with air alsoiiowing in the same direction. After passing through this pipe, the nitrosyl sulfate and air, together with the steamgiven ofi' in a secondary direction from pipe II, are conducted in the primary direction into pipe V, where nitrous anhydrid N203 is expelled from the nitrosyl sulfate, the water is deposited. The aqueous sulfuric acid which is here formed is then passed in the secondary direction through pipe VI, where it gives off its water in the primary direction and flows back as a concentrated acid to pipe III. The vapors from pipes V and VIare combined, and escape' as nitric acid, water and nitrogen, together with an excess of oxygen, which latter can be easily removed subsequently, if, after the condensation of the nitric acid, it is desired to obtain the nitrogen in a pure state. To the pipe system I to VI there are connected four.

to eight pipes A-I-I, of the same kind, the object of which is merely to evaporate the aqueous solution of nitric acid and subsequently to 'condense it again, as far as possible in a quantitative manner, the operations being carried out consecutively in accordance with the `heat exchange principle. In pipe A, water vapor and vapor of nitric acid are generated from a mixture of sulfuric acid,` water and nitric acid -flowing as a secondary current, oxygen being also preferably present. The va orized water and nitric acid are conducte to pipe I, where they ,pass through the stages already described. The aqueous sulfuric acid from A then passes into B, and there fiowing as a primary-current it comes into contact with ,condensed water and nitric acid derived from pipes V and VI and introduced in the primary1 direction and after passing through the tube'is returned with them to lA. For the pur ose of removing the last traces of cxids o nitrogen, the nitrogen '1s conveyed from pi ve B to pipe E, where it 1s heated by asecon ary current of dilute sulfuric acid. Hence it is conveyed in the primary direction into pipe H, where it meets a small amount of steam, 'flowing in the same direction, this steam being that given 'off from pipe II,`in the primary direction. The nitrogen is thus completely purified by water condensation. The liquid in H is renewed asslowly .as possible from pipe A at 150 C. and after traversing H, returns to the opposite side of A, Vnamely that at 120o C.

From pipe III, the oxygen is conveyed into a slowly iowing primary current of dilute sulfuric acid in C, and from the latter it passes in the secondary direction through F, and thence in the primary direction through. G, where it is completely purified in the same way as the nitrogen in pipes E and H. The air required for the process is introduced in the secondary direction into pipe D, in which a primary current of similar composition to that ,in B is slowly flowing.'

Figs. 2-6 indicate the device employed for carrying into practical effect the principle of exchange of heat. p l

In the present process the idea of the invention is to bring about the heat exchange by means of a separate intermediary,

namely by means of a quantity of small solid.

bodies, preferably small balls of equal size which fill the body of the current and oppose the movement of the same, that is to say, in their entirety they represent, with. reference to the current of liquid, a counter current which completely penetrates through the former and thus enable an almost complete heat exchange to be insured. The application of the process necessitates different methods according to circumstances. For example it can 4be restricted to one in which use is made of an intermediate body for effecting exchange of heat between the actual liquid or gaseous current and the heat conducting partition, and in that case it would be suicient to fill the space through which the currents flow with grains of metal, and

to impart also to the grains a gyratory motion about the axis of the currentby giving them space for moving and rotating the system of tubes about its longitudinal axis.

Fig. 2 indicates diagrammatically one form of device suitable for carrying into practical effect an exchange of heat between two liquid currents flowing at constant speed. I

Two hollow cylinders (1) er, b, c, d (axis g, n) and (2) g, 7L, i, k (axis o, p) are filled with identical grains of similar material, for example quarts; the grains lie on perforated bottoms placed close to a, b, or k, a', and fill the cylinders right up to ci, o, or g, h. The liquids which are to be heated or cooled as the case may be, are directed through the cylinders (l) and (2) alternatively in the manner hereinafter described. Considering the cylinder (l) the temperature conditions prevailing therein at the rst stage of the series of operations when the liquid is allowed to enter they cylinder at g are as follows :'-At 1,5 the temperature is T and proceeding along the cylinder it falls uniformly to To at e, f and beyond e, 7 up to d, c the. temperature. is To.

I y At the stagewhen the cylinder (l) is in the condition just discussed, the cylinder (2) has a temperature T between la, z' and Z, m, -which temperature gradually falls to To between Z, mand g, Zt.

The working .of the apparatus is as followst-The hot liquid which. it is desired to cool entersthe cylinder (l) through g and flowing therethrough escapes at the opposite end n, the flow being continued until lthe cylinder becomes heated tosuch an-extent that the regionat the temperature T extends to a, ZJ', from which point the temperature uniformly falls to To at 0l, c. While the hot liquid is flowing through the cylinder (l) 'the cool liquid which it is--desired to Y heat is allowed to flow through cylinder (2) whereby the region at the temperature To is gradually extended until it reaches g', Zt',

whence the temperature uniformly increases' i to T at c,

When this .state has been reached, e. when the transition region or region of intermediate temperatures between T andT0 has moved from a, b, f, e in the cylinder (l) to a', b, c, @Z in the same cylinder,l 'and the transition \region has' moved from g, z m, Z in cylinder (2) to g', Zi', z', 7c, inthe same cylinder then by means of an electric recording thermometer a device is set in motion whichautomatically changes the directionof the hot liquid A lfrom cylinder (l) to cylinder (2) into the latter of which it ows'in thedirection p, o,

and the direction of the. coldV liquid fromA cylinder (2)' to cylinder (1') in which -.it

flows in the direction fn., g When the temperature conditions in the two cylinders have attained theiroriginal state, namely,

a temperature T0 prevailing in'cylinder (l) from e, 7' to .'cZ, c and a temperature T prevailing in cylinder from Z, m to k, i the hot and cold currents of liquid are again automatically changed in directlon soV as to iow through thecylin'ders (1 and respectively. The cycle of flow of the currents of liquids can be repeated any number of times.

The grains transmitting the heat may be given a movement of their own in opposition to the current, so-that each'temperature point retains its fixed place in thenappara'tus'.

This construction is more particularly suitable for liquids which on change of temperature either evolve or absorb gases or i vapors, especially when such volatile ingredients'are to take part 'in parallel or counter current' in the heat exchange.

In order to move the grains' against the current, there could be employed for instance a I,device such as that shown inAFig. 3, which represents a section of-one of the heat exchange tubes through its longitudinal axis. l

In the interior of the tube and normally toits walls is fixed a longitudinal partition r1 r2 r3 r4 T5 r6 1", rs of helical form and perforated like a sieve, so that it easily allows the liquid to passbut keeps back the grains. lf the liquid is guided from right to left,

the grains move, .in accordance with the helical movement, in the opposite direction when the pipe .is -rotated about its longitudinal axis (together with a corresponding 'second branch of the current), in such a manner that r6 passes behind theplane of lthe drawing.

The grains and -liquid preferably lill at the outside one quarter of the tube, while the whole of the remaining space is filled with grains and gases or vapors. This insures not only a better and longer contact of the liquidwith the surface of the grains, but also a satisfactory mixing of the former with the gases and vapors.

.A The grains at the endtof the tube, as shown in Figli, pass (as the device rotates in. the direction of the arrow) through a spiral tube from s over s1 and s2 into a lSiphon with a hydraulics'eal, while the liquidl carried away is continuously returned through a sieve at sl through the pipe s1 s, to lthe starting point, so that when the sieve reaches the position shown in the drawing,

namely the level of the current of liquid in thetube, only the part of the tube from sjto s, remains filled with 'grains and liquid. 1 The latter pipe equalizes the air pressure. From the sipho the grains pass into the corresponding second branch of current for which purpose there could be employed a device, for example like that shown in Fig.

' 5. In the position illustrated in the latter ligure thegrains sink at t, into the discharge pipe t, Z1, t2 (preferably slightly widened at this point) through which they pass, owing to the rotation of the apparatus about u, in

thel direction of the arrow to their point of vwhich above or below the normal temperature at the point at which it is placed closiso.

ing an electric contact which releases the mechanism for raising orlowering the slide. The path of the slide is held free from any 'obstruction by grains by obliquely cutting the surface behind the closing edge ofthe brake-surface, so that it slightly deviates towardlthe direction of movement of the grains. Themovement of the slide can be eected in any desired manner by rotating a rod which` is preferably guided through a narrow tube parallel to the main axis'out of reach of heat and acid. The end of the tube'is closed ii'ian air-tight manner by an annular collar of the4 rotating rod, the surfaces being smeared with vaseline and grinding with a .moderate pressure. Y

If in order tofeconomizef space it is desired to connectrotating steam pipes containing corrosive steamv or` vapors at high temperatures to stationary pipes, this could be done in accordance with the diagram shown in Fig. 6, which isa longitudinal section through a system of concentric glass tubes arranged within each other and sliding or grinding with a slight pressure in one another, the flat cut surfaces being marked 11,02 and "03' '11,. The lines behind the plane of the drawing are marked in dotted lines. The body on the right hand side rotates in such a mannerv that the lowv position comes in front of the plane of the drawing. A tight joint of the ground faces is elected by moisteningvwith sulfuric acid, which, be-

ing supplied through the pipes w vand wp slightly covers the bottom of the tubes.E Any liquid trickling through the ground joints is 4drawn oil through m together with traces of steam, and any liquid penetrating into the conveying pipes y y, during their low position is always pumped' back Aby their elical branch; The helical dam e revents an advance of the liquid, which t erefore4 always must trickle out at v2. If desired the ground joints could be placed behind each other on a-single tapering vided with lateral gasholes.

The materials of which the apparatus .is constructed are as follows The main pipes are made of earthenware containing the largest possible proportion of silicio acid,- sharply bent and provided with an acid glaze, for example, that roduced by melting pyrophosphates. T e pipes can. for

glass tube pro- ,examp'le be made in two lengths connected by pipes of some less refractory-material. The closing cover with the connection branches can be either melted on or pressed with the aid of a slightly glazed surface on a packing oflne platinum wire. The material of the pipes for carrying sulfuric acid Consists of about. 80% lead, and for very high concentration of acids, of cast-iron, vsuch iron preferably containing chromium and silicon, and being provided with a glaze of poly-silicates and basic phosphates and antimonates of tin which by boiling acids.

In order to prevent conduction of heat in the axial direction the system of tubes is are not affected ,longitudinally divided into sections, be-

.tain cases Athese would have to be replaced by enameled metal balls or compositionballs inclosing finely divided reduced metal.-

The whole systemof pipes is mounted on one and the saine spindle and properly packed with asbestos, so that the whole apparatus finally gives the impression of a simple roller about four meters long and two meters in diameter, unless it is preferredto work with smaller dimensions and aconsequently smaller output. The colder pipes are mounted outside. For making up the heat lost, the siphon at 280 can be maintained at the desired temperature, either by electric heating or surface combustion.

What claim as my invention and desire to secure by Letters Patent is 1. The herein described process for obtaining oxygen from the air by a continuous cycle of operations, which consists in producing a high oXid of nitrogen by the action ofl air on a lower oxid, decomposing the higher oxid into oxygen and the lower oxid separating the oxygen from the other products of decomposition of the said higher oxid and thereafter repeating the process i :the lower oxid of nitrogen, and thereafter repeating the process any number of times.`

3. The herein described process for obtaining oxygen from the air by a continuous cycle of operations, which consists in p roducing a high oxid of nitrogen by the action ofair on a lower oxid, reacting the said higher oxid with .hot concentrated sulfuricv acid to form nitrosulfonic ac id, oxygen and water separating and collecting `the oxygen liberated, decomposing the nitrosulfonic acid into sulfuric acid and the lower oxid of nitrogen and thereafter repeating the process any number of times. 4. The herein described process for obtaining oxygen from the air by a continuous cyclev of operations which consists in producing a high oxid of nitrogen by the action ofair on a lower oxid, reacting the said higher oxid with hot concentrated sulfuric acid to form nitrosulfonic acid, oxygen and water separating and collecting the oxygen liberated, decomposing the nitro-sulfonic acid by cooling and the action of water, and thereafter repeatingthe process any number'of times. l

' 5. The herein described process for obtaining oxygen from the air by a continuous cycle of operations, which consists in producing a high oxid of nitrogen by the action of air on a lower oxid, reacting, the said higher oxid with hot concentrated sulfuric acid to form nitro-sulfonic acid, oxygen and water separating and collecting the oxygen liberated, decomposing the nitro-sulfonic acid into sulfuric acid and the lower oxid of nitrogen, and carrying out the reactions in such manner that an interchange of heat can be effected between relatively hot fluids to be cooled, and cool fluids to be heated, by utilizing the heat of a hot fluid for heating a cooler fluid. v

i 6. The herein described process for obtaining oxygen from the air by a continuous cycle of operations, which consists in producing a high oxid of nitrogen by the action of air on a lower oxid, re-acting the said higher oxid with hot concentrated sulfuric acid to form nitro-sulfonic acid, oxygen and water, separating and collecting the oxygen liberated, decomposing the nitro-sulfonic acid into sulfuric acid and the lower oxid of nitrogen, and carrying out the reactions in such manner that an interchange of heat can.

be effected between relatively hot uids to be cooled, and cooled iuidsto be heated byA utilizing the heatfof hot concentrated sulfuric acid for heating coolernitric acid' and water vapor.

7. T-he herein described process for obtaining oxygen from the air by a continuous `cycle of operations, which consists-in pgoducing a high oxid of nitrogen by the action of air on `a lower oxid reacting the said higher oxid with hot concentrated sulfuric acid to form nitro-sulfonic acid, oxygen and waterseparating and collecting the oxygen f liberated, decomposing the nitro-sulfonc acid into sulfuric acid and a lower oxid of nitrogen and providingV an intermediate liquid for effecting an interchange of heat, between a relatively hot fluid, which has to be cooled and .a cool fluid which has to be heated, when the` fluid which has to be cooled and the Huid which has tovbe heated must not come into direct-contact with one another.vv

8. 'The herein described process for obtaining oxygen from the air by a continuous cycle ofoperations which consists in producing a high oxid of nitrogen by the action of air on a lower oxid reacting the said higher oxid with hot concentratedsulfuric acid. to

form nitro-sulfonic acid, oxygen and water separating and collecting theoxygen liber- A 9. The herein described process for ob-` taining oxygen from the air 'by a continuous cycle of operations which consists in producing a high oxid of nitrogen bythe action of air on a lower oxid, reacting the said higher oxid with hot concentrated sulfuric acid to form nitro-sulfo'nic acid, oxygen and Water separating and collecting the .oxygen liberated, decomposing the nitrosulfonic acid into sulfuric acid and a lower oxid of nitrogen and providing small solid particles to act as!" intermediate substances for ei'ecting an interchange of heat between relatively hot fluids which have t'o be cooled and cool iuids which have to be heated.

Y 10. The herein described process for obtaining oxygen from the air by a continuous cycle of operations which consists in producing 'a high oxid of nitrogen bythe action of air on a loweroxid, ,reacting the said higher oxid with hot concentrated sulfuric acid to form nitro-sulfonic acid, oxygen and Water, decomposing the nitro-sulfonic acid, into 'sulfuric acidand a lower oxid of nitrogen and providing small particles of quartz to act as intermediate substances for effecting an interchange of heat between relatively hot fluids which have to be cooled and cool fluids which haveV to be heated.

11. The herein described process for obtaining oxygen from the air by a continuous cycle of operations which consists in reacting` the vapors of nitric acid with sulfuric acid to produce nitrosyl sulfuric acid water and oxygen, decomposing the nitrosyl sul-A furic acid bythe action of water into sulfuric acid and nitrous anhydrid (N203) and combining'the said nitrous anhydrid with oxygen'and water so as to re-form nitric acid, and thereafter repeating the'complete cycle of operations any number of times.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

LUDWIG BERGFELD.

f Witnesses:

ARTHUR J BUNDY, y OTTIME Sm'rz. 

